Use this to mark your own attempt. Accept any correct alternative that answers the question as set. Marks are for the ideas, not the exact words. Unless stated, ecf (error carried forward) applies in calculations. Chermistry practice paper – not an official examination paper.
Total marks: 65 (Section A: 55 marks; Section B: one question of 10 marks)
| Part | Answer and mark points | Marks |
|---|---|---|
| 1 | A – filtration [1]; B – crystallisation [1]; C – paper chromatography [1] One line from each job only. No mark for a job with two lines, or with no line. Reject: A to simple distillation or fractional distillation (the soil does not dissolve, so it is removed by filtration); B to simple distillation (this would not give crystals); C to fractional distillation (this separates liquids, not dyes). | 3 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 2 | A: ✓ correct [1] B: ✓ incorrect and a correct statement: isotopes have the same number of protons (7) and different numbers of neutrons (7 and 8) / different nucleon numbers [1] C: ✓ incorrect and a correct statement: it has 8 protons and 10 electrons because it has gained two electrons [1] D: ✓ correct [1] 1 mark for each student. The tick and, for B and C, the correction are both needed for the mark. Reject for B: “isotopes have different numbers of electrons”; “different numbers of neutrons” with no mention of the same number of protons. Reject for C: “6 electrons” with no correction; “10 protons”. | 4 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 3(a) | • gold: metallic [1] • paraffin wax: simple molecular [1] • calcium carbonate: ionic [1] • Accept “simple molecular (covalent)” for the wax. Reject: giant covalent; “covalent” alone for gold. | 3 |
| 3(b) | a mixture of a metal with (one or more) other element(s) (the other element may be a metal or a non-metal) Accept: a mixture of metals. Reject: a compound of a metal and another element; “two metals chemically combined”; “a pure metal”. | 1 |
| 3(c) | it has no ions and no electrons that are free to move / no charged particles that are free to move; its molecules are neutral (uncharged) Reject: “covalent bonds do not conduct”; “it has no electrons”; “it has no ions” on its own. | 1 |
| 3(d) | the forces of attraction between wax molecules are weak (intermolecular forces), so little energy is needed to overcome them (gold has strong metallic bonding) Reject: the covalent bonds in the wax molecules break; “wax is softer”. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 4 | A: ✓ incorrect [1] and a correct statement: it is a basic oxide because it reacts with an acid to form a salt and water (it does not dissolve in water) [1] B: ✓ incorrect [1] and a correct statement: no gas is formed; the products are copper(II) sulfate and water (hydrogen forms only when an acid reacts with a metal) [1] C: ✓ correct [1] For A and B the tick and the correction are marked separately, but a correction scores only if the claim is ticked incorrect. Reject for A: “it is a basic oxide because it is a metal” with no reaction with acid. Accept for A: “it reacts with (dissolves in) acid but not in water”. Reject for B: “oxygen is formed”; “carbon dioxide is formed”. | 5 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 5(a) | B has twice as many hydrogen ions in the same volume / B has twice the concentration (A has half the concentration of B) / B has 8 hydrogen ions and A has 4 Reject: “B has more hydrogen ions” with no comparison of the volume or the concentration; the reverse. | 1 |
| 5(b) | • B has the greater rate [1] • more hydrogen ions per unit volume (particles closer together), so more frequent collisions between hydrogen ions and zinc atoms (more collisions per second) [1] • The second mark needs the answer B (or an ecf from a wrong answer in (a)). • Reject: “more collisions” with no reference to time or frequency; “the particles move faster” or “have more energy” (the temperature is the same); “more successful collisions” alone. | 2 |
| 5(c) | 2 hydrogen ions drawn in the box (half of the 4 in A), drawn anywhere above the zinc, not touching each other badly Reject: any other number of ions. Ignore the exact positions as long as the ions are inside the box. | 1 |
| 5(d) | exothermic and the temperature of the mixture increases (from 22.0 °C to 31.5 °C) / heat is given out to the surroundings Both the type and the reason are needed. Reject: endothermic; “the reaction produces a gas”. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 6(a) | photosynthesis Reject: respiration; combustion. | 1 |
| 6(b) | combustion / burning (of the fuel / diesel) Reject: respiration; photosynthesis; “burning of oxygen”. | 1 |
| 6(c) | methane is a greenhouse gas: it traps heat / infrared radiation, so the atmosphere warms up (global warming / climate change) Accept: more extreme weather; melting of polar ice; rising sea levels. Reject: acid rain; damage to the ozone layer; “it is toxic”. | 1 |
| 6(d) | ethanol + oxygen → carbon dioxide + water Both reactants and both products are needed. Reject: carbon monoxide; hydrogen as a product. | 1 |
| 6(e) | the carbon dioxide released when bioethanol burns is taken in by the growing sugar cane (by photosynthesis) / the sugar cane took in carbon dioxide while it grew, so there is little net increase Reject: “bioethanol does not produce carbon dioxide”; “it produces less carbon dioxide” with no reason. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 7(a) | • 1: ✓ incorrect and P contains iron(III) ions (the precipitate is red-brown, not green) [1] • 2: ✓ correct [1] • 3: ✓ incorrect and R contains zinc ions (the white precipitate also dissolves in excess aqueous ammonia; aluminium hydroxide would not) [1] • 4: ✓ correct [1] • Both the tick and (for rows 1 and 3) the correction are needed for the mark. Reject for row 1: iron(II) with a different reason; for row 3: “calcium” or “aluminium”. | 4 |
| 7(b) | • P: sulfate [1] (white precipitate with barium nitrate) • Q: nitrate [1] (no precipitate with silver nitrate, so not chloride; none with barium nitrate, so not sulfate) • R: chloride [1] (white precipitate with silver nitrate) • Accept formulae. Reject: carbonate. | 3 |
| 7(c) | • correct formulae of all reactants and products [1]; balanced [1]; correct state symbols [1] • Fe(NO3)2(aq) + 2NaOH(aq) → Fe(OH)2(s) + 2NaNO3(aq) • Accept the ionic equation Fe2+(aq) + 2OH−(aq) → Fe(OH)2(s) with state symbols. Missing or incorrect state symbols lose the third mark only. A wrong formula loses the first mark; the balancing mark may still be awarded. | 3 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 8(a) | 40 + 2 × (14 + 3 × 16) = 164 | 1 |
| 8(b) | 8.20 ÷ 164 = 0.0500 mol (ecf from (a)) | 1 |
| 8(c) | 0.0500 ÷ 0.250 = 0.200 mol / dm3 (ecf from (b)) 250 cm3 = 0.250 dm3. Reject 0.000200 or 200 (volume not converted from cm3 to dm3). | 1 |
| 8(d) | 8.20 ÷ 0.250 = 32.8 g / dm3 or 0.200 × 164 = 32.8 (ecf from (a) or (c)) | 1 |
| 8(e) | 0.200 × 0.0500 = 0.0100 mol (ecf from (c)); or 0.0500 × 50.0 ÷ 250 = 0.0100 50.0 cm3 = 0.0500 dm3. | 1 |
| 8(f) | • the ratio is 1 : 1, so 0.0100 mol of calcium carbonate is formed [1] • 0.0100 × 100 = 1.00 g [1] • ecf from (e). Mr of CaCO3 = 40 + 12 + 3 × 16 = 100. | 2 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 9(a)(i) | CnH2n Reject: CnH2n+2; CH2. | 1 |
| 9(a)(ii) | any value from 85 to 105 °C (higher than hex-1-ene, with a gap of about 30 – 35 °C that follows the shrinking gaps in the table: about 95) Reject any value outside this range. | 1 |
| 9(a)(iii) | liquid and room temperature is above its melting point (−119 °C) and below its boiling point (about 95 °C) ecf from (ii): any boiling point above 25 °C gives liquid. Reject: gas; solid; a reason with no state. | 1 |
| 9(b) | • burning produces carbon dioxide, a greenhouse gas, which adds to global warming [1] • incomplete combustion produces toxic carbon monoxide (and soot / toxic fumes) [1] • Accept any two different valid reasons: carbon dioxide / greenhouse gas; carbon monoxide / toxic gas; soot or smoke (air pollution). Reject: “it makes acid rain”; “it uses up oxygen” alone; “the film is useful”. | 2 |
| 9(c) | C6H14 Accept C6H14 written in any correct form. Reject: C6H12; C6H16. | 1 |
| 9(d) | • many small molecules (monomers) join together to form one very long molecule (polymer), with no other product [1] • ethene has a C=C double bond, one bond of which opens (breaks) so that each molecule can join to the next / ethene is unsaturated [1] • Reject: “polymers join together”; “a double bond becomes a triple bond”; a statement that water is lost. | 2 |
| 9(e)(i) | poly(ethene) is not biodegradable / does not rot (so it stays in the soil for a very long time) or it harms animals that eat it / it blocks drains and waterways Any one. Reject: “it is hard”; “it is made from crude oil”; “it takes up space” alone. | 1 |
| 9(e)(ii) | melt the plastic and remould it / make it into pellets that are used to make new objects (a physical method) or crack it into smaller molecules for use as fuel / chemicals (a chemical method) Any one method. Reject: burning it; burying it; “reusing” with no method. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 10(a) | • magnesium is the most reactive (first) and copper is the least reactive (last) • zinc is more reactive than iron (zinc before iron). Correct order magnesium, zinc, iron, copper = 2 marks. Accept symbols (Mg, Zn, Fe, Cu) or the letters of the metals. Reject: the order reversed (least reactive first). | 2 |
| 10(b) | hydrogen (accept H2). Reject: hydrogen ions; hydrogen chloride; oxygen. | 1 |
| 10(c) | copper is unreactive / does not react with water (or with acids) / is low in the reactivity series, so the pipe is not attacked by the water. Reject: copper is a good conductor of heat or electricity; copper is strong; "copper does not rust" on its own. | 1 |
| 10(d) | magnesium is more reactive than copper and iron / is higher in the reactivity series, so it is harder to obtain from its ore (accept: its compounds are more stable; it holds on to oxygen more strongly; more energy or a more difficult method is needed). Both the comparison of reactivity and the link to difficulty are needed. Reject: magnesium is rarer; magnesium is a lighter metal; magnesium is less reactive. | 1 |
| 10(e)(i) | the more reactive the metal, the higher the temperature needed (accept: the temperature increases as the metal becomes more reactive; the least reactive metal, copper, needs the lowest temperature). Reject: a statement about one metal only; "the temperature increases" with no link to reactivity. | 1 |
| 10(e)(ii) | any temperature above 500 and below 800 °C, e.g. 650 °C (accept the unit omitted). Reject: 500 °C or below; 800 °C or above (lead lies between copper and iron). | 1 |
| 10(f) | • calcium ion drawn as [Ca]2+ in square brackets with the charge 2+, with either no outer electrons or eight outer electrons shown (the electron arrangement 2.8.8) • two chloride ions, each drawn as [Cl]− in square brackets with the charge 1− and eight outer electrons: seven of one symbol (its own) and one of the other symbol (from calcium) • Accept all electrons shown as dots or all as crosses if the transfer is still clear; accept the ions in any order. Do not credit: a shared pair or a covalent bond; one chloride ion only; a missing or wrong charge (the mark for that ion is lost); a chloride ion with fewer than eight outer electrons. | 2 |
| 10(g) | from 0 to +2 (both values needed). Accept: increases by 2; 0 to 2+. Reject: +2 to 0; a change for oxygen (0 to −2); "increases" with no values. | 1 |
| Part | Answer and mark points | Marks |
|---|---|---|
| 11(a) | • four answers: P hydrogen; Q iron(II) chloride; R iron oxide; S rust (accept hydrated iron(III) oxide). • All four correct = 2 marks; two or three correct = 1 mark; one or none correct = 0. • Accept formulae H2, FeCl2, Fe3O4 (accept iron(II) oxide, iron(II,III) oxide or triiron tetraoxide for R; reject iron(III) oxide, which is red-brown like rust). Accept iron chloride for Q. Reject: iron hydroxide for R; hydrogen chloride for Q; iron(II) chloride or iron for S. (Equations: Fe + 2HCl → FeCl2 + H2; 3Fe + 4H2O → Fe3O4 + 4H2; reaction 3 is iron with oxygen and water.) | 2 |
| 11(b) | bubbles / effervescence / fizzing / a gas is given off; accept: the iron gets smaller / dissolves; the solution turns pale green. Reject: hydrogen is formed (a name is not an observation); the iron melts; the solution turns brown. | 1 |
| 11(c) | iron reacts with steam and with (dilute) hydrochloric acid but copper does not (under the same conditions), so copper is less reactive. Both parts of the comparison are needed. Reject: copper is a metal; copper is unreactive (with no comparison with iron). | 1 |
| 11(d) | harder, because potassium is more reactive than iron (higher in the reactivity series), so its compounds are more stable / it holds on to oxygen more strongly. Both the prediction (harder) and the reason are needed. Reject: easier; potassium is rarer; potassium is a softer metal. | 1 |
| 11(e)(i) | the plastic forms a barrier / layer (over the iron) that keeps oxygen (air) and water away from the iron. Accept: oxygen and water cannot reach the iron. Reject: plastic is more reactive than iron; keeps out air only or water only. | 1 |
| 11(e)(ii) | painting; greasing / oiling (accept galvanising, as a barrier). Reject: plastic coating (stated in the question); keeping the iron dry (no barrier); any answer with no method. | 1 |
| 11(f) | • two double bonds: two shared pairs of electrons (each pair one dot and one cross) between the carbon atom and each oxygen atom • each oxygen atom has two non-bonding pairs (lone pairs), so eight outer electrons including the shared pairs; carbon has eight outer electrons and no lone pairs • Accept all electrons shown as dots or all as crosses if the shared pairs are clear; accept without outer circles. Do not credit: ions drawn; two single bonds; a triple bond; oxygen atoms with fewer than eight outer electrons. | 2 |
| 11(g) | iron (accept Fe), because it loses electrons / gives electrons to the hydrogen ions (so the hydrogen ions are reduced). Both the identification and the reason are needed. Reject: hydrogen ions (they are the oxidising agent); iron(II) ions; hydrogen. | 1 |